Why have an axle that doesn't touch the road?
March 13, 2025 7:30 AM Subscribe
I see this every so often: a truck or trailer has an axle with wheels off the ground. Example (the axle behind the fuel tank). What's this axle for?
Posted before I noticed how remarkably similar the Wikipedia example photo is to yours !
posted by Perplexity at 7:39 AM on March 13
posted by Perplexity at 7:39 AM on March 13
Best answer: If you're not hauling a very heavy load-- you don't need to spread the weight over so many wheels/axles, so you raise that 'spare' axle up to save you fuel. They'd be hydraulic so you can lower/raise them from a panel in/around the truck.
posted by Static Vagabond at 7:39 AM on March 13 [1 favorite]
posted by Static Vagabond at 7:39 AM on March 13 [1 favorite]
Best answer: axle up to save you fuel
And tolls too, where the price is based on number of axles.
posted by 922257033c4a0f3cecdbd819a46d626999d1af4a at 8:07 AM on March 13 [4 favorites]
And tolls too, where the price is based on number of axles.
posted by 922257033c4a0f3cecdbd819a46d626999d1af4a at 8:07 AM on March 13 [4 favorites]
Best answer: Truck Topia video explanation of lift axle.
posted by 7 Minutes of Madness at 8:08 AM on March 13
posted by 7 Minutes of Madness at 8:08 AM on March 13
Best answer: Really short answer from former truck driver and commercial auto insurance adjuster: they’re to equalize weight distribution for safety, road wear, and legal compliance (Like on a scale where your weight per-axle matters). You put it down for a heavy load and put it up when empty. You also put it up when you’re on uneven pavement, esp when you’re a concrete mixer with rear floaters bc a low shoulder or pile of road debris will grab your rear float and flip you, and then you’ll have to dispose of a cylinder of dried cement (aka easter egg).
posted by toodleydoodley at 8:45 AM on March 13 [10 favorites]
posted by toodleydoodley at 8:45 AM on March 13 [10 favorites]
I have always wondered this, but usually while I am driving and thus not able to Google it myself!
posted by jacquilynne at 9:48 AM on March 13 [2 favorites]
posted by jacquilynne at 9:48 AM on March 13 [2 favorites]
Response by poster: Thank you! I couldn't even figure out the right term to search for.
posted by mkb at 12:06 PM on March 13 [1 favorite]
posted by mkb at 12:06 PM on March 13 [1 favorite]
It’s funny, the Wikipedia article says “lift axle,” but I’ve only known them as “floating tandems.” TMYK right?
posted by toodleydoodley at 4:58 PM on March 13
posted by toodleydoodley at 4:58 PM on March 13
Back in the day, we called them "Tag Axles."
nth all the bove.
posted by mule98J at 7:36 PM on March 13
nth all the bove.
posted by mule98J at 7:36 PM on March 13
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posted by Perplexity at 7:38 AM on March 13 [7 favorites]